2. It provides a convenient way for participants to keep track of where to find the questionnaire, and how much they have already completed. Participants sometimes don't have time to answer all of the investigator's questions in one sitting. The ePRO system keeps track of how much participants have already done and it's ready to keep going whenever the participant has time. It also avoids the common problem of losing the questionnaires to the household paperwork pile, or worse to the recycling bin.